1. Field of the Invention
The present invention relates to a honeycomb structured body.
2. Discussion of the Background
In order to purify exhaust gases discharged from internal combustion engines of vehicles, construction machines and the like, such as buses, trucks and the like, a honeycomb catalyst that allows the exhaust gases to pass through the inside thereof to purify the exhaust gases has been used. Conventionally, for example, there has been proposed a honeycomb catalyst having a structure in which a high specific surface area material such as active alumina and the like and catalyst metal such as platinum and the like are supported on a surface of a cordierite-based honeycomb structured body that has an integral structure and a low thermal expansion property. There has been also provided a honeycomb catalyst having a structure in which an alkaline-earth metal such as Ba or the like is supported thereon as a NOx occlusion agent, so as to be used for treating NOx in an atmosphere with excessive oxygen such as an atmosphere in a lean burn engine and a diesel engine.
Here, in order to improve the purifying performance, it is necessary to increase the possibility of contact between exhaust gases and the catalyst noble metal as well as the NOx occlusion agent. For this purpose, it is necessary for the support to have a higher specific surface area and for the noble metal to have a smaller grain size and to be dispersed in a high level. Therefore, there are suggested honeycomb structured bodies in which the cell shape, the cell density, the thickness of cell walls, and the like have been devised (for example, see JP-A 10-263416).
With respect to the honeycomb structured body made of a high specific surface area material, a honeycomb structured body that has been subjected to extrusion molding together with inorganic fibers and an inorganic binder has been known (for example, see JP-A 5-213681). Moreover, in order to allow such a honeycomb structured body to have a large size, a structure in which honeycomb units are jointed to one another through an adhesion layer has been known (for example, see DE 4341159).
Moreover, there has been disclosed a honeycomb filter in which a Young's modulus of an adhesive layer is set to 20% or less of a Young's modulus of a honeycomb unit (for example, see JP-A 2001-190916). The contents of JP-A 10-263416, JP-A 5-213681, DE 4341159, and JP-A 2001-190916 are incorporated herein by reference in their entirety.